In recent years, vast strides have been made in the field of computer-assisted image processing. The creation and manipulation of images has proved a boon to many engaged in the graphic arts field, industrial monitoring, and surveillance, but there are still problems in the initial stages of rendering an already existing image into processable form. The classic approach to securing a computerised image is to scan a photographic original to form a file in which data are stored representing properties of a large number of portions of the image, so-called pixels. Each pixel is characterised by a number of parameters corresponding to colour and intensity, and the file contains data relating to the location of each pixel so that when the file is called up by an appropriate program, the image is displayed on screen. Most recently, the process of scanning has been supplemented by the development of so-called digital camers, which produce an image file directly.
In order to process the image to the form desired by the user, it often needs to be broken down into different parts, for example those corresponding to background and displayed object, in order to change the colour balance of the background without affecting that of other parts of the image. This process of segmentation is time-consuming and requires a high degree of skill. Attempts to automate the process have been made, but they do not work well or easily, as the intellectually comprehensible pieces of an image, clear to any human viewer, are simply not easily identifiable by a computer.